# File: backend/app/services/assistant_service.py (Update with DB)
# Description: 管理助手数据的服务 (使用 SQLAlchemy)

from typing import List, Optional
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.future import select
from sqlalchemy import update as sqlalchemy_update, delete as sqlalchemy_delete
from app.db.models import AssistantModel
from app.models.pydantic_models import AssistantCreate, AssistantUpdate, AssistantRead

class AssistantService:
    """助手数据的 CRUD 服务 (数据库版)"""

    async def get_assistants(self, db: AsyncSession) -> List[AssistantRead]:
        """获取所有助手"""
        result = await db.execute(select(AssistantModel).order_by(AssistantModel.name))
        assistants = result.scalars().all()
        return [AssistantRead.model_validate(a) for a in assistants] # Use model_validate in Pydantic v2

    async def get_assistant(self, db: AsyncSession, assistant_id: str) -> Optional[AssistantRead]:
        """根据 ID 获取单个助手"""
        result = await db.execute(select(AssistantModel).filter(AssistantModel.id == assistant_id))
        assistant = result.scalars().first()
        return AssistantRead.model_validate(assistant) if assistant else None

    async def create_assistant(self, db: AsyncSession, assistant_data: AssistantCreate) -> AssistantRead:
        """创建新助手"""
        # 使用 Pydantic 模型创建 DB 模型实例
        db_assistant = AssistantModel(**assistant_data.model_dump())
        # ID will be generated by default in the model
        db.add(db_assistant)
        await db.flush() # Flush to get the generated ID and defaults
        await db.refresh(db_assistant) # Refresh to load all attributes
        print(f"助手已创建 (DB): {db_assistant.id} - {db_assistant.name}")
        return AssistantRead.model_validate(db_assistant)

    async def update_assistant(self, db: AsyncSession, assistant_id: str, assistant_data: AssistantUpdate) -> Optional[AssistantRead]:
        """更新现有助手"""
        update_values = assistant_data.model_dump(exclude_unset=True)
        if not update_values:
            # If nothing to update, just fetch and return the existing one
            return await self.get_assistant(db, assistant_id)

        # Execute update statement
        stmt = (
            sqlalchemy_update(AssistantModel)
            .where(AssistantModel.id == assistant_id)
            .values(**update_values)
            .returning(AssistantModel) # Return the updated row
        )
        result = await db.execute(stmt)
        updated_assistant = result.scalars().first()

        if updated_assistant:
            await db.flush()
            await db.refresh(updated_assistant)
            print(f"助手已更新 (DB): {assistant_id}")
            return AssistantRead.model_validate(updated_assistant)
        return None # Assistant not found

    async def delete_assistant(self, db: AsyncSession, assistant_id: str) -> bool:
        """删除助手"""
        # Prevent deleting default assistant
        if assistant_id == 'asst-default': # Assuming 'asst-default' is a known ID
             print("尝试删除默认助手 - 操作被阻止")
             return False

        stmt = sqlalchemy_delete(AssistantModel).where(AssistantModel.id == assistant_id)
        result = await db.execute(stmt)
        if result.rowcount > 0:
            await db.flush()
            print(f"助手已删除 (DB): {assistant_id}")
            # Deletion of sessions/messages handled by cascade="all, delete-orphan"
            return True
        return False